text:
Does auto pilot take into consideration the altitude, speed, and the difference in heading change, to calculate the degree of bank?
Or is there a “standard” that the auto pilot follows at all times?
By “standard” I mean the aircraft will bank at x amount of degrees each time regardless of the following mentioned? The more you bank, the sharper the turn is, correct?

A standard what?

I'm guessing what you're after is the formula between airspeed and bank angle for a standard rate turn, which is:
std_bank_angle = arctan( pi / 60.0 * TAS[m/s] / 9.81[m/s/s] ) for a one minute (60 second) 360° turn

You may also read about close feedback loop. Here, you want to maintain heading controlling bank angle.

If your talking about standard rate turns, those are not really practical in large commuter aircraft. As true airspeed increases the maximum turn rate decreases when the bank angle is limited to a comfortable level of less than 30 degrees of bank. So please make this question more specific, which airplane category are you talking about?
Usually the autopilot uses the difference between the target heading and the current heading to generate a bank angle target, often just proportional by a linear factor but limited to, e.g. 25 degrees of bank or the minimum of a 30 degree bank turn and a standard rate turn bank angle or even manually selected like in the Boeing aircraft.
The autopilot then calculates the difference between the target bank angle and the actual bank angle and generates a roll rate target. Based on the roll rate target and current roll rate the autopilot computes a roll acceleration target and finally an aileron deflection target, which could, for example, just be a factor times the roll rate deviation.
The computation from the deviation of any of these parameters to the next lower level control loop target can consider the true airspeed and altitude, yes. But this can't be said for all types of autopilots that ever existed and is too broad of a question.
For certification of an autopilot system it has to be demonstrated that the autopilot remains within a safe enveloped, as specified in the requirements. This could limit the roll acceleration, roll rate, maximum bank angle or demand a response within a certain time frame or a maximum deviation for any of these values, transient allowed overshoots, etc. Since the autopilot has to work throughout the flight envelope the parameters used in the computation of the bank angle, roll rate, roll acceleration, aileron deflection, etc. may require a look-up table for each airspeed and altitude to ensure a stable and safe operation.
This can differ between aircraft types, e.g. a large passenger aircraft should fly less aggressive roll maneuvers because the people sitting on the outside far away from the center are being subjected to major g-forces as the aircraft rolls, which is uncomfortable and potentially hazardous.

In all the jets I fly,  the autopilot will always bank at 25 degrees.  It doesn't worry about standard rate turns.  As others have pointed out or alluded to; a standard rate turn with airspeed above 180 KTAS requires larger than comfortable bank angles.
The autopilots also have a half bank feature to limit banks to 13 degrees.  Most often pilots will use that feature on a single engine climb at V2.
Some FMS installations will also limit its bank angle above a certain altitude to half bank to limit the chance of an acceleration stall.  The autopilot must be in NAV mode for that to work.

The amount of bank is that which is required to achieve the standard "Rate 1" or 2 Minute turn, being 3 degrees heading change per second, which takes you in a full circle in 2 minutes.  This is a universal protocol for turns in the IFR world.
This varies with true airspeed (the faster you're going the higher the bank angle required to turn at 3 deg/sec) but you get a good ballpark number by dividing TAS by 10 and adding 7 (so at 180 kt, it's 18 + 7, or 25 degrees bank).
The pilot hand flying a light aircraft has the Turn and Bank or Turn coordinator to determine when the bank angle is correct for Rate 1 and flies whatever bank angle gets the indicator showing the correct rate.  The pilot of a transport aircraft has the Flight Director to tell him/her the precise bank angle target required.  (If the turn rate indication or Flight Director indication was not available, that's when the 10% of TAS + 7 formula comes in handy.)
The autopilot does the same thing. It uses whatever bank angle it needs to to achieve Rate 1, and it'll be programed to use a certain roll rate and roll out lead heading angle (normally quite gentle - several seconds to roll into a 25 deg banked turn).  It'll start to roll out of the turn about 15 degrees of heading before the target and reduce the roll rate as it gets close to creep the last few degrees to avoid overshooting.
The amount of heading change doesn't really come into it, unless the heading change is so small that it's time to start rolling out before the turn rate even gets to Rate 1.


text:
Did the First Officer of Ethiopian Flight 302 trim in the wrong direction?

Looking at the accident report of Ethiopian Airlines Flight 302, it says the cut out switches were used. But the manual trim moved from 2.3-2.1? My reasoning for asking this is because the timeframe on this specific input is 5:40:42-5:43:11 which goes up to the point the crew re engaged the electric trim motors. It sounds like they’re being vague for a reason. Did the First Officer trim in the wrong direction and then tell his Captain “It’s not working”?

@ymb1 While I agree with you that speculation about the pilot's actions is off-topic, all the various questions asked in the body are generic enough to be on topic (it seems the accident report was more of a motivation to ask them). Maybe the question title can be rephrased accordingly?

Im not sure what the issue is? I’m just getting into aviation lately and find it really interesting. I’m not trying to shame pilots at all, I’m just asking an honest question, I don’t see the harm in speculating about it either. It’s nice to see the knowledge some people can spread. As far as asking basic trim questions, I guess I’ll stop posting them.

Questions that can only be answered by speculation are defined as being off-topic here. Some forums allow participants to engage in speculation about aircraft accidents, but Av.SE does not. It's a choice about what type of forum is desired. This one is less about discussions and more about facts. Others take a different approach, and having both flavors available on the internet is, in my view, a good thing.

@RalphJ hi Ralph. What forums are you talking about exactly? Here on stack exchange or elsewhere?

@Firefighter1 very much elsewhere. If you read the link in ymb1's comment about what's on-topic and what's off-topic for [aviation.se], that will answer your question.

@FreeMan no I’m asking what forums around the web allow this kind of discussion? I haven’t found any.

@Firefighter1 I'm not sure if it's explicitly on topic, but there is loads of speculation  at the AV Herald

On the Boeing 737 the trim wheels are directly connected to the stabilizer jackscrew with cables. The force required to move the trim wheels depends on the load on the stabilizer. The more you are out of trim, the more force is required to move the stabilizer.
From the 737 NG FCOM (9.20.8 Flight Controls - System Description - Stabilizer Trim, emphasis mine):

Manual stabilizer control is accomplished through cables which allow the pilot to
  position the stabilizer by rotating the stabilizer trim wheels. The stabilizer is held
  in position by two independent brake systems. Manual rotation of the trim wheels
  can be used to override autopilot or main electric trim. The effort required to
  manually rotate the stabilizer trim wheels may be higher under certain flight
  conditions. Grasping the stabilizer trim wheel will stop stabilizer motion.

left: trim wheel with handle stowed (source), right: jackscrew in the tail (source)
The FCTM (8.17 Non-Normal Operations) explains the correct procedure for manual stabilizer trim (emphasis mine):

Runaway Stabilizer
Hold the control column firmly to maintain the desired pitch attitude. If
  uncommanded trim motion continues, the stabilizer trim commands are
  interrupted when the control column is displaced in the opposite direction.
Manual Stabilizer Trim
If manual stabilizer trim is necessary, ensure both stabilizer trim cutout switches
  are in CUTOUT prior to extending the manual trim wheel handles.
Excessive airloads on the stabilizer may require effort by both pilots to correct the
  mis-trim. In extreme cases it may be necessary to aerodynamically relieve the
  airloads to allow manual trimming. Accelerate or decelerate towards the in-trim
  speed while attempting to trim manually.
Anticipate the trim changes required for the approach. Configure the airplane
  early in the approach. When reaching the landing configuration, maintain as
  constant a trim setting as possible. If a go-around is required, anticipate the trim
  changes as airspeed increases.

Note: this FCTM is from a 737 NG, not a MAX. The part about "trim commands are interrupted when the control column is displaced in the opposite direction" is no longer true when MCAS is active on the MAX, the rest is still valid though.
You can also see this procedure applied in this YouTube video by Mentour Pilot.

Regarding the Ethiopian crash: I don't want to speculate on what the crew did, but if

the stabilizer position gradually moved in the AND direction from 2.3 units to 2.1 units

then it did indeed move in the wrong (AND - Aircraft Nose Down) direction.

It's more or less the same trim system a J-3 Cub or Cessna 180 has, but with electric motors added.

@RobertDiGiovanni The 737 stab trim units (I don't think it is in degrees) range from 0 (APL NOSE DOWN) to about 17 (APL NOSE UP). You can see them on the scale next to the trim wheel.

It may be helpful to see airspeed, trim and AOA data from from the entire event (from take-off roll).  And the load sheet too.

@RobertDiGiovanni It is (partially) in the accident report: see page 26 of the PDF.

Fully reading the report was helpful, see page 12/33

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text:
Why do pilots wait for a positive rate to put the gear up, When V1 means “commit to takeoff”?
To explain further, V1 means they cannot stop in time if anything happens. Therefore they must commit to taking off. So why wait for a positive rate? Shouldn’t it be retracted as soon as they see a difference in altitude? From my understanding, is that the landing gear deployed during a crash landing can rupture the fuel tanks??

V1, you're still on the ground!

This question could be clarified by saying "So why wait for the VSI to show a positive rate of climb?"-- if that's what you meant.  Arguably, if you see any indication of change in altitude in the correct direction in the altimeter hands, digital altitude readout, symbolic tape depiction of altitude, etc, you are in some sense seeing an indication of a positive rate of climb, so your question as written is a little unclear.  The distinction between seeing a positive change in altitude indication and seeing a "positive rate" is not obvious.

@Fattie well aware. What I mean is why wait to put the gear up when V1 means if a problem occurs it’s an inflight emergency.

V1 is the speed at which you are committed to take-off, it doesn't mean you are off the ground. You can't retract the gear at V1 because you are still rolling on it heading down the runway.
Vr is the speed at which you rotate the nose up to get into the air. Again you are still rolling down the runway with your nose in the air, you can't retract your wheels if you are using them.
V2 is the speed at which you are able to climb with one engine inoperative. It doesn't mean you are in the air yet, you can't retract the gear.
And just because the main gear come off the ground doesn't mean a gust won't push you back down, so usually you leave it down until you are reasonably assured that you won't touch again. It's a lot gentler on the aircraft if you touch the wheels than if you rub the skin off the aircraft. Positive rate is pretty much the only indication of this since there is a little bit of a lag in the VSI, by the time it shows positive rate you are far enough off the ground that you really don't need to worry about touching again.

Shouldn’t it be retracted as soon as they see a difference in altitude?

The best indication is not the altimeter, it is the VSI. It reacts faster than the altimeter.
For GA aircraft, a lot of pilots won't retract the gear until "there isn't any runway left". This means that taking off on an 8,000 foot runway, they would be airborne by the 1500 foot mark and leave the gear down in case the engine fails they can just put it back down again.
What you really don't want to happen is for the gear to be retracted prematurely. When you are rolling down the runway you get "light on your feet" and the gear retraction mechanism can pull the gear up before the aircraft is ready to fly. The squat switches may be unloaded so they won't stop the system. Best thing to do is to wait for the positive rate, verify visually and then retract. Personally I leave it down until I'm 500' below pattern or no more runway left.

Thank you for your answer! I appreciate the knowledge.

The radar altimeter should be faster than the VSI but since the attitude of the aircraft can also affect the reading this is not really reliable. It would also show increasing figures as the terrain below you drops off, doesn't mean that you're actually climbing... And you sated correctly the barometric altitude is way too slow and so the vertical speed indicator is used as the best option.

In all big air craft, the retraction cycle involves the opening and extension of many bay doors where the gear is stored. Practically it means that initially you will experience an increase in drag when the gear is retracted. We do not want this when close to ground.

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text:
Does the NTSB and other investigative agencies charge airlines for investigations?
Does an airline have to pay the investigation team? For example the NTSB? And if Boeing or Airbus participate in the investigation, do they also charge the airlines?

I assume because you said NTSB, you are asking about the United States?

Indirectly (through taxes)

Related

I don't think Investigations must be done with financial rentability in mind, thus it should be financed on public founds only.

How does it work for a multi-jurisdiction investigation, such as Air France 447 or MH370? Is the main investigator the country where the plane took off/ crashed/ the plane was registered in?

In the United States, no, the airline does not pay the NTSB or the FAA for accident investigations. This is considered a public service and is paid for by tax funds.
That doesn't necessarily mean that they won't pay for anything. For example if the NTSB has to remove wreckage to examine it, they will often have the insurance company pay for the removal and transport. This is especially true in GA investigations where the responsibility for moving the wreckage (after the NTSB says so) is up to the owner/their insurance.
Whether or not Boeing/Airbus/XXX charges airlines would be another matter that is probably outlined in contracts between the airlines, the aircraft leasing company, and the manufacturers.
Note that NTSB may involve any number of parties, for example they would have Boeing for the airframe, GE for the engines, Honeywell for the avionics/sensors, and representatives from other companies/groups (like the Airline Pilots Association) as they see fit. NTSB has manufacturer representatives for the bigger parts, and may ask for additional help from other smaller providers. This is done under the NTSB "party system" which is by invitation and does not compensate the parties for participation.
So as far as accident investigation goes, no, airlines/manufacturers don't pay for that directly.

The OEM will have its own Product Safety organization, staffed with investigators and analysts, that participates and supports accident investigations with its own internal contingency budget.  So when a crash happens, a team is formed with the Regulator (FAA), the Gov't Investigator (NSTB), investigators or representatives from the OEM, and investigators or representatives from the affected airline, with everybody paying their own way.


text:
What kind of warranty comes with a commercial aircraft?
Just wondering what the warranty is like. Can an airline simply decide to give every single aircraft back for the money they paid? Assuming they were unhappy with the results.
Will the manufacturers cover any repairs and regular service of the aircraft for x amount of time after the delivery?

I have had direct experience with this and yes new aircraft are sold with a warranty like a car, say for 3 years or 5 years and x hours.  The OEM may maintain local service centers, and a/c under warranty may be sent there for moderate fixes, although most of the time the airline fixes the problem itself and charges back the OEM for labour and gets parts provided by Spares free of charge (to the extent it's worth their while to do so for labour chargebacks; sometimes the administrative hassle to recover, say, 5 manhours at an overhead allowance of 50 or 60 bucks an hour isn't worth the trouble).
In extreme cases problem aircraft have been known to have been taken back by the OEM to prevent an angry operator from canceling a large ongoing order, or some such situation where it's important to mollify the customer.
Sometimes the OEM will use in-house product support teams to go out and do more significant work on aircraft under warranty, especially if the airline doesn't have the resources in-house, for free.
The OEM's program office will have a warranty administration group that manages all this.  A significant sum of money is budgeted by the OEM to cover warranty reimbursements and you could say this is built into the price (I dimly recall that on the Regional Jet program there was a budgeted warranty allowance of about a quarter or half a million $ per aircraft, but it may have been more than that).
Once it's out of warranty, well, you're on you own buddy.  You'll pay for spares, and for support from the OEM beyond basic help desk advice.  Major mods may or may not be provided free of charge to out of warranty a/c, depending on how nearly broke the OEM is budget-wise, or how much the bad publicity will hurt.  An airline may get satisfaction, on old out-of-warranty costs it was unhappy about, as part of a package negotiated on a new aircraft sale.  This is common on re-orders where airlines add more aircraft to an existing fleet.
Airlines may also negotiate (if they're smart) "AD clauses" where the OEM agrees to pay parts and labour for work required under a mandatory AD, with it's own, later, expiry date.

As always, a great answer from you! Thank you John.

Thanks. I've had the personal experience of watching my boss get yelled at by angry operators over this sort of thing many times (they were always nice to us foot soldier tech geeks though, so it was mostly entertaining).

No lemon law on aircraft?

Can you imagine?  I used to observe a very interesting dynamic at conferences. US operators would publicly complain and demand satisfaction pretty much on behalf of all operators. They wanted everybody to get the same treatment.  European operators wouldn't pound the table like that.  They would approach quietly to arrange sidebars to cut their own deals.  Over time US operators started to abandon public egalitarianism for the private meeting approach when they saw that the former wasn't working and the latter got better results.


text:
How is DME station ident coded in ARINC 429?
I understand that labels 242,244, 246, 247 are set for DME Station Id or DME Station Ident. they are marked as discrete. How should I convert the station code from alphabet to these 'discretes'? The station codes are something like AGG.

Labels 246 and 247 describe up to 4 7-bit ASCII characters.

1th char: Bits 11-17 of 246
2th char: Bits 19-25 of 246
3th char: Bits 11-17 of 247
4th char: Bits 19-25 of 247

For AGG, in ASCII we get 0x41, 0x47, 0x47, then:

Label 246 = 0x11D04A6
Label 247 = 0x11CA7

SSM encoding is the same as regular discrete labels.
I am not familiar with labels 242/244.


text:
Do experienced pilots look at the inclinometers during flight?
I have been researching on the use of rudder during flight e.g. during turns and noticed that several novices have issues using the rudder to achieve coordinated turns.
Often, I see comments stating that the "sense" on the use of rudder will develop over time / rudder use becomes second nature sooner or later / you should turn based on seat of pants etc
Question: Do experienced pilots of single engine propeller aircraft actually look at the inclinometer or do they solely use their "senses" to make coordinated turns? If they do use their senses, does that mean that "stepping on the ball" is no longer applied when you become experienced?

Yes to some degree but it depends a lot on your seating position.  If your torso is fairly upright and not too well supported, slips and skids become easy to sense, beyond a certain point, as your waist muscles have to work to keep up upright as you "lean into the ball".
With experience it's possible to stay within, say, half a ball width of centre, without looking at it.  It's tougher if the airplane has reclined seats or has seats with strong side bolsters that hold you in well.
That being said, you still need to glance at the ball it to keep it really centred while maneuvering and I tend to use both my leaning sense and glances at the skid ball at the same time, leaning sense for large yaw excursions and the skid ball for fine tuning.
It's a good skill to master when VFR flying because you can keep your head outside the cockpit where it belongs (in VFR) a lot more.
Gliders use a yaw string for skid control and because you are steeply reclining the leaning sense is fairly useless and you rely mostly on the string, which is easy because it's right in front of your face and you don't have to put your head down.
In any case, you still "step on the ball" or "step toward the lean".  It helps to develop the automatic foot action so you squeeze the pedal with your foot instinctively whenever you move the ailerons.  Pilots who learn on gliders have this action fully automated.

I have 900 hours.  I still look at the ball as part of the over all instrument scan.  The ball is colocated with 20 degree bank indicator as well, so I know when I making smooth, coordinated standard rate turns.  Keeps me in practice for flying in IMC also.

Thanks so much for your reply! As an experienced pilot, would you say that rudder use is somewhat second nature and scanning the inclinometer just gives you an indication on whether your "rudder sense" is accurate? Or do you actively look out for the ball to adjust your rudder?

My plane has the rudder linked to the ailerons somewhat, so for shallow turns I don''t need much rudder input at all and I'll just glance at the ball.  For tighter turns, I'l control it more and I'll look at it more, especially when the weather is rougher.  Especially in IMC - gotta keep up your scan in case an instrument fails, always be cross checking.

My old Cardinal was a '68 and it didn't have the rudder interconnect.  The adverse yaw wasn't too bad, but it required a bit more footwork than a 172.

@ymb1 You are correct that it measures a standard rate turn, but the bank angle of a standard rate turn is related to airspeed. If you are flying an approach at 100 kts then a standard rate turn requires about 15° of bank. At 120 kts it is 18°. My guess is that CrossRoads is flying at around 125kts. Luiz Monteiro (among others) has a post explaining the math behind it. http://www.luizmonteiro.com/Article_Bank_Angle_for_Std_Rate_01.aspx

I mostly fly Piper Cherokees, what's a 'rudder'?   :)


text:
Calculating Lift of a closed-wing drone
A group of students and I are designing a theoretical closed-wing drone and need to calculate lift based on the NASA lift equation. We've designed fixed-wing aircraft before and when it came to finding the co-efficient of lift for the airfoil, we just used the NACA charts. Since the aircraft will be closed wing this time around, we are not entirely sure how to go about this. We are very amateur, so I know we are likely missing very obvious things. Thank you for any help that can be provided.

Have you tried AVL?

@Jimmy I tried googling it, but the page for a consulting firm came up.

Athena Vortex Lattice. You probably want to read up on what vortex lattice is and how it computes. The AVL manual is also good.

@Jimmy Thank you! This looks like it might be just what we need!


text:
When to start descent entering a racetrack under NORDO?
Scenario:
I am flying in IMC, and communications fail completely. IMC persists up until destination, where I will be conducting the following instrument approach:

I am flying direct to ZUNAD from the north, approaching it on a track of 200°. When within the prescribed MSA, I descend and maintain 4,300 ft. At the moment I reach ZUNAD, I will be performing a teardrop entry into the racetrack/procedure turn (heading of 211° after ZUNAD for one minute, then right turn direct to ZUNAD).
Question:
Can I start descending to 2,600 ft just after passing ZUNAD, entering the procedure turn on that heading of 211°, or should I wait until I cross ZUNAD again and become established on the racetrack pattern?

You can descend from 4300' to 2600' as soon as you pass ZUNAD, as long as you remain in the protected airspace of the hold at ZUNAD.
It is the same situation if you were "Cleared for an approach" in a non-radar environment.

But if you're cleared for an approach sans radar coverage, the controllers can at least still hear you, and vice versa, while the situation in the OP involves a complete loss of all radiocommunications.

It depends on what you filed in your flight plan. To what point were you cleared? The key word in AIM 6-4-1,a.3. is “ When the clearance limit is a fix from which an approach begins”.

(c) Leave clearance limit.
(1) When the clearance limit is a fix from which an approach begins,
commence descent or descent and approach as close as possible to the
expect further clearance time if one has been received, or if one has
not been received, as close as possible to the Estimated Time of
Arrival (ETA) as calculated from the filed or amended (with ATC)
Estimated Time En Route (ETE).
(2) If the clearance limit is not a fix from which an approach begins,
leave the clearance limit at the expect further clearance time if one
has been received, or if none has been received, upon arrival over the
clearance limit, and proceed to a fix from which an approach begins
and commence descent or descent and approach as close as possible to
the estimated time of arrival as calculated from the filed or amended
(with ATC) estimated time en route.

A good practice would be to include the IAF, IF and/or FAF in your flight plan. If the clearance limit is the airport, you have to go to the airport first before you proceed to the fix to hold until the ETA.
Some people say to make the IAF, IF, or FAF the last point on your flight plan. In a safety forum with DFW TRACON(D10), the controllers in attendance stated they do not prefer that method. Since, that does not make clear your actual final destination. They prefer the airport to be your last point (block 16 in the ICAO flight plan form).
If you place a fix with a published hold in your flight plan, you can delay your arrival either by holding or by slowing your airspeed until close to the ETA. Then, you can just land via the approach as normal.
Either way, ATC will clear the airspace at that airfield at your ETA until you call to close your flight plan. If they do not know which approach you are going to use, they will clear all the approaches for that airfield.
P.S.
Since KHQM is a Class E airfield, there is one caveat if you are in inadvertent IMC without a plan. You CAN proceed directly to a landing by any safe means necessary, including the above mentioned approach. When NORDO in IMC land, as soon as practicable.
I would recommend you circle directly above the airfield at 1000 feet above TPA (or higher if surrounded by high terrain) as a good form and a safe practice. A few laps around the airspace, high enough to be in radar contact, should alert ATC of your presence and possible intentions.
You can do the same at a Class D. You just have to fly far enough away or high enough to remain in Class E or G airspace until you receive light signal clearance directions from ATC.


text:
How to get registration from ICAO 24 bit code?
The description of PlanePlotter claims that it can determine the registration letters from the ICAO 24 bit address algorithmically for some countries.
The only thing i got so far is how to get the country. Any clues?
Edit:
After some more research I found some information in the book "Principles of Avionics" by Albert Helfrick:

Generally, there is no algorithm giving a one-to-one correspondence
  between ICAO 24 bit addresses and the registration number of the
  aircraft. Some ICAO member states did have an algorithm that would
  translate ICAO 24 bit aircraft addresses to registration numbers but
  ICAO strongly suggested the practice to stop.

Algorithm for swedish registrations: http://www.transportstyrelsen.se/publicdocuments/PDF165.pdf

Maybe some countries have a system and the people at PlanePlotter reverse engineered them?

Do you have a link to this claim?

http://www.coaa.co.uk/planeplotter.htm "PlanePlotter can can determine the registration letters algorithmically, from the 24-bit hex address"

Is there anyway to tell if the aircraft is rotary or fixed wing from the ICAO 24-bit address?

Apparently (according to these folks) some countries use an algorithm to generate their ICAO (Mode S) 24-bit IDs. For those countries, you can simply reverse the algorithm and get a registration given the Mode S ID.
Others countries allow you to download their registration database, complete with the Mode S identifier (you can get the US registration database here) - it's a simple matter to load this into your own software and map the ICAO/Mode S ID code to a registration number.
As the folks at Gatwick Aviation Society have noted, some countries are tight-lipped about how their codes are assigned (and who they're assigned to), so these lookups are probably not complete.

The Mode_S closed-group on Yahoo Groups has documented many of the allocation algorithms.
https://groups.yahoo.com/neo/groups/Mode_S/info
Apply to join and explain your motivations.  They have an extensive Files section.

There are no algorithms documented in the Files section of that group that I can find, only lists of ,<algorithmically generated registration #>

Not only are there no algorithms in that Files listing, but the listing for Belgium is very incomplete and contains lots of tail codes that are not even allowed - all the ones starting with Q for example.

Some countries use a deterministic formula (e.g. US, Japan, South Korea), others use do not. There are about a dozen or two that do have a formula. Take a look at the popular ADS-B decoder dump1090's decoding logic.

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text:
What is the most efficient design for a human powered aircraft limited to 30mph at 100ft?
What is the most efficient design for an aircraft limited to a maximum velocity of 30mph at a maximum altitude of 100ft?
The objective is to minimize drag and weight.
The payload would be 1 human, and my budget is approximately 100,000 dollars (more can be done) for materials I was thinking airloys (because they are light and strong). The end goal is to go more than 74 miles on flat train using human power.
My guesses are aircrafts shaped like a sail plane or a Ground Effect Vehicles (GEVs).

Payload and function would also be important design factors.

I added important details is it enough to re open the question?

@mins For a human-powered aircraft, wouldn't the range be mostly a function of how long it takes the pilot to get tired/hungry?

This question still seems very broad. What kind of 'efficiency' are you talking about? Just the least power input on the part of the human to sustain flight? If it's that, wouldn't the answer basically just be "Use a glider and forget the human-powered part?"

@Frvgdf Keep explaining - this question still isn't really answerable. Your details add some context but they also don't help the question if you're truly asking about efficiency rather than constructing an aircraft.

@mins Ah, so I see. I guess I should have looked at the edit history first.

@mins yeah sorry I was meaning human powered but there are plenty of human powered aircraft that look like sail planes but there are not very many that look like GEVs so I did not know if I would be able to get an awnser if I said human powered

@reirab when I ask about efficiency I am asking about the least drag and weight how would you say I phrase that?

@digitgopher so I am asking about the most effecent normal aircraft so that I can possibly apply some of the principles of that aircraft (except for getting into thin air to reduce drag that can not be done) and apply them to a human powered aircraft.

It looks like you're asking something that normally takes a team of engineers to answer, and judging by the variety of aircraft out there, ten engineers will give you eleven different answers.

It would probably be shaped something like Daedalus:  https://en.wikipedia.org/wiki/MIT_Daedalus

authors: عمر الجامودي

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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How do acrobatic pilots avoid pulling too many G’s and passing out?
I just watched a video of a acrobatic pilot doing stunts, it involved a type of stall, not sure which one though. Long story short he overcompensated(?) which caused him to pass out, and then he crashed in the lake. Honestly I’m surprised this doesn’t happen more often. What kind of safety measures do they take when pulling off maneuvers that come close to the ground and would require a fast change in angle of attack?

Is this the Red Bull Air Race pilot who just clipped the water,  or are you talking full on crash? Unrelated but your title and question body seem to ask 2 different questions. WHich did you want answered?

@Jamiec oh I meant to ask the same question as the title. No it didn’t look a Red Bull pilot. Video looked old, but this nailed the water. I didn’t read too far into it but I’m sure he died. He almost hit a boat too

You might be interested in watching the William Wyler documentary "Thunderbolt!", which shows a P-47 pilot blacking out when recovering from a dive bombing run. You can find it on Netflix and I think on YouTube.

@FredLarson thank you! I’ll have to take a look!

There are certain things you can do to increase your G tolerance without a G suit, mostly static tension exercises like squeezing your diaphragm, lower torso and thigh muscles, isometric exercise style, to slightly slow down the blood flow to your legs during the pull.  Plus just really good physical fitness so your body can handle weighing 4 or 5 times normal for short periods (neck muscles are critical for this, more so if you're wearing a helmet).
Beyond that, and without a G suit, it's just awareness of how hard you can pull and knowing where to ease off.  You have a G meter in the plane to indicate where you are, but if experienced you should be able to tell within reason by the sensation.
You start to lose your vision (grey out) before you pass out completely, so that is a key warning sign that you'd better back off right now.  However someone who pulls too hard too fast may pass through the grey out period to pass out phase too quickly and it's lights out for a bit.   In the end, the pilot just misjudged and screwed up, probably by getting himself into a situation where the choice was to pull too hard or hit the ground.
Great link provided by a commenter for more info.

Some good material on this [PDF]: https://www.faa.gov/pilots/safety/pilotsafetybrochures/media/acceleration.pdf

Thanks! I added it as a link to the body since the comments aren't part of the "permanent record".


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What should a pilot flying IFR in IMC and on final, do if the vacuum system fails?
Talking about small aircraft here, assuming the pilot is stable and ready to land, they’re flying IFR and the visibility is nonexistent, but that’s alright because he’s currently IFR! But then the vacuum system fails. The pilot loses:
 Attitude Indicator
 Heading Indicator
 Turn Coordinator
With a very poor visibility I can see how this could end up fatal. What is the do’s and don’t here? I can easily see that with every scenario there can be an argument for both “do” and “don’t”. Pilot could go around, but at the same this may not be smart because you don’t know the pitch of the plane, at the same time I see it being okay because you know airspeed.
I can also see a reason to continue on, to try and see if you can visualize the runway and land, seeing you know your altitude, at the same time I can see how that can be disastrous. So what’s the correct way to go about this type of failure in horrible conditions?

The attitude indicator and turn coordinator you have pictured say either "DC" or "DC Elec" on the face plate, indicating that these specific versions are electrically driven, not vacuum driven.

Loss of electricity in this case, would represent one of the worst scenarios. You could till fly partial panel. You would have to pay close attention to the DG, Altimeter, and VSI. These would have to serve to indicate pitch changes as well as turn and bank. Keep all inputs very minute. Keep all banking very shallow. This would hardly ever be the case since the Attitude Indicator and the Turn Coordinator are usually not on the same power source for the reason of that they both are key to banking information.

GdD’s answer is accurate (up vote). My answer will be more step by step.

The first thing you should do is recognize the issue. That might not be immediately easy depending on your aircraft and it’s electronics suite. If there is no visual and auditory alert, you will have to wait for the gyros to wind down to a certain extent.
Immediately announce to yourself and the rest of the flight crew which instruments are inop. Even solo, you should be talking to yourself out loud. It activates the auditory part of the brains learning and response mechanism. Most of us are a combination of visual, auditory, and kinesthetic.
Cross check your other instruments.
Ignore the inop instruments and utilize your back up instruments.
Stabilize your descent per the IAP.
Declare an emergency. In IMC this is an emergency situation. This should be quick, simple, and to the point. For example, just state, “Mayday! Mayday! Mayday! [callsign] has lost instruments!” Don’t bother going into details at this point. It will just confuse matters. And, you don’t have the time. Plus, not all ATC are pilots. They may not know the significance of partial panel, lost vacuum or lost gyro. Just say “instruments”. ATC might have a lot of questions to ask you about the nature of your emergency. Fly the airplane first. Put your concentration into the approach. Then, talk to ATC. You can sort out the details when you have time. Once the opportunity arises, you can make a proper call like, “[airfield tower or CTAF]. [callsign]. [distance & direction from field]. Inbound on final. I’ve lost primary flight instruments. Landing full stop runway [#]. Declaring an emergency. I need a field advisory.“ The last part is a last minute double check of field conditions, wind, and any other unforeseen issues. Remember, this is under the assumption that you are already on or close to being on final (like on or intercepting the intermediate leg), and have already been making the appropriate radio calls.
Have another crew member cover the inop instruments.
Continue the approach.
If you see the runway, and it’s possible to, LAND.

That last part is a judgement call. The situation will dictate what you do. Some may say only land if you meet all the normal criteria, since a go-around is the default for all descents and approaches. Although this is true, you are in an emergency situation. Land if at all possible. Go missed only if it is not possible to land.  For instance, if you are landing a four-seater four-banger on a 10,000 foot runway. And, you are in a position to safely land it on the last quarter of the runway, do so.
Also, Stratus is a great, last ditch, unofficial, non-certified back up. Its AHRS function can be accessed through EFB apps like ForeFlight or through its own proprietary app. Although it can not be used as a source of navigation or instrumentation, it would be better than nothing in a pinch.

Your second action point is probably one of the most underrated (or maybe even one of the least known) best practises of aviation. Talk to yourself, keep yourself informed. The communicate part of aviate, navigate, communicate also means communicating with yourself. There are huge psychological advantages in announcing your findings and intentions out loud, even if you are by yourself. Silence is not golden in aviation.

Exactly. It activates the auditory part of the brains learning and response mechanism. Most of us are a combination of visual, auditory, and kinesthetic. I added that to my response.

I like this answer best.  Key point from the question:  "You are stabilized and ready to land" when you go partial panel.  This is actually the very best scenario for it to happen!  Partial panel sucks.  We all practice it, but you want to minimize your exposure.  Climbs, turns, speed changes, configuration changes, switching nav equipment, etc. are all things you would prefer to avoid.  Just keep the wings level and try to stay on course, watch your VSI and altimeter, and pray you break out...

Excellent point. Plus, you can ignore your DG and AI if your NavCom (and/or GPS) and Altimeter are working. Your turn coordinator can even be inop (if it is not electrical). Although this increases the complexity and risk exponentially. Although, careful monitoring of your mag Comp can mitigate this.

Partial panel training for me was to have the instructor “fail” the MFD and PFD. This left me with an Electric Attitude Indicator, Altimeter, Airspeed Indicator (some times), Tachometer, Mag Comp, and a Garmin 430W on the Default Nav page (no moving map nor rate-of-turn/turn coordinator). When the instructor would also “fail” my Airspeed Indicator, I would have to rely on the Tach using GPS ground speed as a double check. Training also included all phases of flight as well as upset recovery. Each two hour session would leave me wiped out.

Your scenario isn't really realistic, the turn coordinator and the AI are almost always on different sources of power to protect against this very event. The TC is almost always electrically driven because it gives an alternate source of information.
A loss of an instrument or even a whole suite of instruments is something instrument rated pilots train for, and should practice once they have their rating. We call it partial panel, where you use your other instruments to make up for the loss. If you lose your vacuum driven instruments you fall back on your electrical and non powered instruments like the altimeter, airspeed gauge, VSI and magnetic compass.
Addressing your question, if I experienced a loss of vacuum on short final when I was established on an instrument approach I would most likely simply continue the approach and land. A loss of vacuum doesn't immediately cause those instruments to keel over and die, they keep working for awhile, getting less accurate as they spin down. Heck, if I'm on a short final I may not even recognize the failure!
If I'm on a longer final and I lose my vacuum powered instruments I would also continue the approach unless there was alternative with better conditions or less hazards nearby. Your vacuum instruments aren't going to fix themselves, so there's no point in flying around waiting for something else to go wrong.
The exact situation you describe in your question would be extremely unusual to say the least, this would most likely be caused by something pretty catastrophic that would mean continuing the approach is impossible. If I had a total powered instrument failure but somehow my ILS and radio stayed up I would continue the approach using the residual momentum of the gyros to keep situational awareness as long as possible, then fall back to my working instruments. I'd also declare an emergency, and ask for ATC to give me surveillance radar data, they can give me a running commentary of which direction I'm turning.
Of course, if it was me I'd activate emergency AI app I have on my tablet GPS or my phone. Both use the phone/tablet sensors to produce a pretty reliable picture.

Buy one of the devices that gives you GPS plus AHARS, and make sure that it’s calibrated with ForeFlight and your iPad on EVERY FLIGHT. THen in the bizarre situation that your vacuum AND electric fail simultaneously you can STILL land using just your iPad. Oh... and for sure check this by flying an approach with an instructor and failing ALL instruments to make sure that you can really maintain control in this scenario.
ForeFlight + independent GPS and AHARS is an amazing resource.

Yes, Stratus or Sentry.

Yeah, but as per question you'd have to land with partial panel before you can go shopping for pads and stuff.

@Jpe61 I think the idea of the answer is to buy this and have it with you now, before your instruments fail in IMC. :)

Plus request a "No Gyro" approach from ATC or request vectors to an airport that has that capability if you have fuel to make it there.

No-gyro or Radar Approaches are a great tool if you have a loss of instruments. I would hazard against prolonging time in IMC by going to another airport if the one you are at does not have radar capabilities. If you have a working NavCom and/or GPS you should be able to shoot an approach just as well with only those and an altimeter. The more time you spend in IMC going to another airport is more time to lose spatial orientation. Use No-gyro only as a last resort in case you have no navigational ability or equipment at all.


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How to not converge or diverge from the runway when there aren't checkpoints?
When flying circuits under VFR, if there is no clear distinct checkpoint available, what can you do/use as a checkpoint? I suspect the runway but please correct me if I'm wrong. How do you make sure you don't converge, diverge from the runway or stray away from the centreline?

Guys, thank you so much for the feedback. But I think I may have used the wrong word or phrase in "checkpoint". I think the actual phrase I was looking for was "reference point". The "reference point" (at a distance) at which when you takeoff, you use to maintain a straight and constant heading. The "reference point" at which you use, just before you turn, to turn onto and again, maintain a heading. Your feedback would be greatly appreciated once more.

I'd like to add something to Ron's answer.  Use of geographic checkpoints is used a lot in initial training but it can become a debilitating crutch that leaves you in the lurch as soon as you go to another airport.  I teach in gliders where getting the circuit right is fairly critical the first time, there being only one chance to land.
The really important checkpoint or turnpoint is the turn from downwind to base.  Learn to recognize the presentation of the runway when at a 45 degree aspect to it, which is normally the proper turn point for downwind-to-base unless you are extending or shortening your downwind for a specific reason.  I always weaned my glider students from dependence on geographic points as soon as possible, and certainly before solo.
You are at 45 degrees to the runway when the extended line of the lengthwise edge and an extended line of the threshold are "even" relative to the horizon.   This can be pretty tricky to discern at first but over time you'll learn to recognize this just by the appearance from your vantage point, and you will no longer care about ground landmarks.

I assume by checkpoints you mean visual cues for position. A "checkpoint" is different in the aviation world and is used by VFR pilots to report locations to controllers. These are denoted with a "Flag" on VFR maps.
The runway you are landing on is really all the visual reference you need. When flying a circuit you take off and follow centerline, which means you use the heading as a reference and add any cross-wind correction to stay on track. This takes some practice so don't be discouraged if you start drifting with the wind. Adding the appropriate cross-wind corrections directly after your wheels leave the ground is a skill, and then realizing that it changes about 50-100 feet above the ground is another skill.
300 feet below pattern altitude you should start your cross-wind turn. Usually by the time you get to pattern altitude it is almost time to turn downwind. The goal when you turn downwind is to be about 1/2 mile from the runway. In a 172 at pattern altitude, this means that the runway will cross your strut about half-way up (provided your seat is adjusted properly, this is important in flying patterns/landing).
The next "checkpoint" is mid-field downwind. This is when you start running your landing checklist. After that your next checkpoint is when the runway touchdown zone is about 45 degrees behind you, this is when you start your base turn and descent.
The last tricky turn doesn't really have a "checkpoint", the goal is to turn from base to final and roll out on extended centerline. You need to take into account if you have a tail wind or a head wind. For a tail wind you want to turn sooner, a head wind you'll turn later. Again this is a skill that comes with time. Extending your downwind can give you more time to correct any alignment errors. Starting your downwind too early will cause you to overcorrect or overshoot the turn.
After that your eyes should be focused on airspeed, altitude, and aiming point.
Really these are just a skill you develop as you train. Don't expect to be perfect in the first 20-30 landings/take-offs. Some pilots require hundred(s) to master the skill... Then they change aircraft and have to start again.


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How do I know when to read a number as (for example) 241 or 24.1 off the navigation computer?
How do I know in what way I should read a number off the naviagtion computer scale on the slide rule side?
Eg. 241 and 24.1

What do you mean by "navigation computer"? An E6B, or something else?

If you are talking about an E6B, you follow the same rules for your result as you followed for your inputs. If you used a factor of 10 for your inputs, you use a factor of 10 for your results. If all else fails, you use the common sense rule. For your particular calculations, does 241 make sense? Or, does 24.1 make sense?


text:
What happens during a solo checkride and how do I put myself in the best position to be successful?
What happens during a solo checkride and how do I put myself in the best position to be successful?
Also, why is it 2 hours? Is there a reason it would be longer than the flight you're used to if you usually fly 1.5 hours?

This seems pretty broad to me...

Okay, let me try explain where I am. So far, for my flight training, I've been flying with an instructor. For every single flight so far, I've flown with an instructor. I am currently on Ex. 12, 13E. My instructor booked me with a Grade II instructor and on the booking it said "Check", so I'm just trying to find out what I can expect during this flight.

You haven't soloed yet? I'm assuming that you are on an accelerated training program, otherwise that's a bit early to be scheduling your exam! Have you asked your instructor what's involved? In any case this really is too broad and there's a lot of opinion in it.

It's pretty simple.  You will be asked to demonstrate everything you've learned.  The Grade II is evaluating you and is also evaluating your instructor's teaching skills.  The two hour block probably includes extra time allowance if the check instructor wants to give you remedial or supplemental training before signing you off (assuming you are acceptable), and the actual flight may be the full 2 hours or quite a lot less.
Just relax and do what you're told to the best of your ability and don't worry about it. To best prepare, go through all the things that you may have to recall from memory, especially emergency memory items or sequences or mental check lists, and drill drill drill that stuff on the ground while at home or while driving until you can't stand it any more, then do it some more.  You want to be able to spit out procedures or numbers automatically without thinking, under pressure, with distractions, and to do that it just takes repetition (have a friend shove you and yell at you while you recite everything - you'll know right away if you have things internalized sufficiently).
I cannot stress that aspect enough.  If you have everything that needs to be memorized fully burned in to your brain beforehand, it will massively reduce the stress of the flight itself and you'll find you are better able to free your brain to concentrate on flying and it's only a matter of having the physical and judgement skills in place or not.
The other thing to add is that instructors and examiners love students who show up well prepared, who have obviously taken a lot of time and effort to learn what they need to learn, who can spit out answers to verbal questions immediately without having to mull the question over (to a reasonable degree).  The result is that they will tend to cut you a bit of slack on little screw ups you make during the evaluation or test if it's obvious you are putting in the work, and obviously, aren't dangerous.  In the end they just need to be satisfied you won't kill yourself, and a lot of that comes from a general feeling of comfort the examiner gets from the overall experience of flying with you and knowing what you have put into it.


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How does density altitude affect performance, temperature, and pressure; and how is it calculated?
I'm trying to better understand density altitude. If the density altitude at Rand Airport (for example) is 8300 ft:

What does the 8300 ft mean? Does it mean that at that altitude, aircraft performance will be at its lowest?
What does the 8300 ft mean in terms of air quality? Does it mean that at that altitude, the pressure will be at its lowest and the temperature at its highest?
And why 8300 ft specifically? Was it calculated? If so, how?

The International Standard Atmosphere (ISA) gives “average” values of air pressure and density by altitude. It starts by defining standard pressure 1013.25 hPa (29.92 inHg) and standard temperature 15°C at sea level, and derives the values for higher altitude from physical laws.
A “density altitude” is altitude in ISA at which air has the density you are observing. This is analogous to “pressure altitude”, which is altitude in ISA where the pressure you are observing occurs.
You can measure pressure altitude easily by setting your altimeter to the standard pressure of 29.92 inHg/1013 hPa. However you don't have any instrument to directly measure air density, so you have to calculate density altitude from pressure altitude, temperature and humidity.

And why 8300 ft specifically? Was it calculated? If so, how?

This AOPA document provides approximate formula:

Density altitude in feet = pressure altitude in feet + (120 x (OAT - ISA temperature))

Pressure altitude is determined by setting the altimeter to 29.92 and reading the altitude indicated on the altimeter.
OAT stands for outside air temperature (in degrees Celsius).
ISA stands for standard temperature (in degrees Celsius).

Keep in mind the standard temperature is 15 degrees C but only at sea level. It decreases about 2 degrees C (or 3.5 degrees F) per 1,000 feet of altitude above sea level.

I have also found a calculator, which uses more accurate equation, also taking humidity into account. It comes with detailed explanation of the physics involved.
Giving it current METAR FAGM 301600Z 33006KT CAVOK 27/00 Q1022 it calculates density 0.967 kg/m³, which is expressed as density altitude 7 866 ft (2 397 m).
It's already late afternoon, so earlier in the day it might have even 8 300 ft (if it was 31°C, which might have been just past noon)

What does the 8300 ft mean in terms of air quality?

It is simply another way of expressing the density 0.954 kg/m³. You are normally familiar with how the performance decreases when you climb, so expressing density as altitude allows you to easily reference the loss of performance due to the hot weather to that.

What does the 8300 ft mean? Does it mean that at that altitude, aircraft performance will be at its lowest?

It means aircraft performance will be as if you were at 8 300 ft on a standard day.
Both aerodynamic and engine performance depend on density. For aerodynamic performance higher density altitude means you'll need higher true airspeed for the same indicated airspeed, and for engine higher density altitude (lower density) means lower maximum power.
For an average single-engine piston aircraft, 8 300 ft is quite high. The performance will be poor.


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What engine should I use for a home-built ultralight (That is rideable)
I am looking for an engine that is powerful + cheap engine that will work in an ultralight aircraft and fly 1 person as well as the plane. yeah, this is kinda specific, but I have a tight budget and want it to be safe.  thanks a lot if you can solve this for me!

Your best bet is to go with a motor developed for paramotors with all the grief of development already accounted for.  They are big on static thrust and use small engines with simple and reliable reduction drives running fairly large propellers, mostly 2 stroke although there are some 4 strokes available now, like the EOS (if you want really decent reliability, you really need to go with 4 stroke).  Root around in the paramotor world on the intertubes and educate yourself.
For an ultralight, you would just need to use a propeller with more pitch than used in paramotors due to the higher speed range, but otherwise these motor packages are ideal.  You could purchase a used paramotor cage unit just for the motor/reduction drive for probably a lot less cost, for decent reliability, than the alternatives.

This is a homemade UltraLight airplane being tested with two pilot with different weight: 70kgs and 120kgs. It is using Simonini Mini Evo 2 (just use Google translate to translate the discription there).
Simonini Mini 2 EVO: a 2-strokes single cylinder engine, 33HP (or 25kW) at 8000rpm. Dry weight: 19.3kgs. Made in Italy. This engine is quite cheap, most used for paramotor as John K explained in his comment.
An equivalent engine is Rotax 377. It is 35HP engines @6500RPM. Weight: 34kgs. This is seems stronger than the Simonini as lower RPM, but heavier. Made in Austria. Unfortunately, it is no more in production.


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Why do UCAV/UAV designs mostly use lambda wings instead of pure delta wings?
Why do recent UCAV/UAV designs mostly use lambda wings (such as Taranis and Dassault nEUROn) instead of pure delta/diamond wings (such as X-47A Pegasus and Lockheed D-21)?
As for stealth characteristics, both wings have a direct advantage in radar wave reflection.

The image was taken from Technology challenges of stealth Unmanned Combat Aerial Vehicles (Sepulveda & Smith, 2017).

Radar receiver is at where the transmitter is. As long as the wave don't reflects back, nobody cares how the wave scatters from the rear.

@user3528438 A radar receiver and transmitter are not necessarily colocated. Welcome to the world of Multi Static Primary Surveillance Radar

Aspect ratio.
Look at your two images: both wings offer the same wingspan, but the former requires a lot more wing area for it. Wing area is weight. More wingspan for less wing area means better fuel efficiency and thus better range.
Poor aspect ratio, leading to excess induced drag, is a major disadvantage of delta wings. Much of modern stealth design is an effort to mitigate the poor flight characteristics of early "stealth-only" solutions.
Neither UAV nor UCAV get meaningful benefit from supersonic flight, since they can't realistically oppose manned fighters. Large UAV and UCAV are meant for long-range predictable stealth missions, where slow and steady wins the race. Better fuel efficiency means more payload or longer-range missions, both directly improving the vehicle's usefulness.


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Is it safe and effective to have "glider pilot mentality" when landing single-engine fixed-wing aircraft?
I am a low-time pilot, of approximately 200 hours. I trained on the DA20 and DA40, designs that are derived from the Diamond touring motor glider design(s) of the early 1990s. I anticipate getting my Glider rating this summer in the US. As I've considered getting my glider rating, I've noticed a habit that I've developed that closely matches the "glider pilot mentality" which does not seem so prevalent in my training for ASEL.
I've always preferred using a forward-slip for landing with the engine idle, as opposed to using the throttle to adjust the descent angle. I attribute this to multiple factors, such as being aware of the design history of the DA20, training with its more "glider-like" characteristics, and a general paranoia of the engine quitting on base or final.
This brings me to the following questions: What are the safety considerations for this type of approach? Are there limitations on the use of sideslip on light airplanes?
Edit: Supplement questions, for possible merge or replacement of above. (Taken from my comment below)

Instead of puttering in using throttle, why don't we use side slips all the time?
Why don't most/more GA aircraft have spoilers or dive brakes?
Is the mentality of "every landing is an engine-out landing" creating more danger than it alleviates?

For what it's worth, in my experience in the U.S. from the late 1950s through the 1990s, we used slips in aircraft with flaps almost exclusively for crosswind correction rather than for altitude correction. However, I was taught how to use slips for altitude loss, and would occasionally do so for practice, typically leaving the flaps up. I did still use slips for altitude loss in a Piper J-3 in the 1960s that didn't have flaps. Regardless of the aircraft type, we had no reluctance with regard to using the engine for glidepath control.

The edits to remove the opinion based elements are good, but I feel that they change the question substantially from the original.

The spirit of the question is basically: "Instead of puttering in using throttle, why don't we use side slips all the time?" which may evolve into the question "Why don't most/more GA aircraft have spoilers or dive brakes?" . My mentality is that every landing is an engine-out landing, such that when I have a real engine-out emergency, it is no big deal. Is that mentality creating more danger than it alleviates?

For low-performance airplanes, flaps are employed instead of drag devices because they also provide lift and help the airplane meet the Vs0 requirement of 61 knots. High-performance retracts may have drag devices if they need airspeed control in certain regimes of flights (bombing, descent, approach, and landing). My airplane has speed brakes, but they are used only in descent and are ineffective on landing. Every glider you are likely to fly has some kind of drag device.

Some related questions that may shed some light as well: Is it safer to do a regular approach than a short approach?, Why is “dragging it in” considered bad in small aircraft, but fine in larger aircraft?, Why is flying in a slip uncomfortable?, What happens in a stall during a slip?, On crosswind landings, is it preferable to side slip or crab on final approach?

@Lnafziger excellent list, will be busy reading those.

Diamond aircraft are very low drag and do not have particularly effective flaps, so sideslipping is certainly an effective way to approach the problem. However there are considerations you need to be aware of:

A steeper approach can bring you down on top of another airplane on final approach. Maintaining a more common approach angle is safer as it is less likely to bring you into a potential collision, and keeps you on a path where other pilots are likely to see you
Steep sideslips are not particularly comfortable for passengers, the steep angle and different feel can be frightening
Having your engine idle for long periods can lead to ice buildup in your carburetor, even with the heat on. It also lets your engine cool down quite a bit. Keeping some revs on keeps things warm up front
A steep approach angle makes it harder to round out accurately
A mishandled sideslip can lead to a loss of control. If the ball is to one side and you get past the critical AoA you will be executing a snap roll at low altitude, which = bad

There's nothing wrong with using sideslip and keeping up with the technique - it's very useful if you catch a thermal on approach, are given a slam dunk approach, or need to get on the ground fast. For me it's not the best tool for normal approaches when you have alternatives, especially if you come in at a very steep approach angle.
One technique I've heard of for approaches on Diamond single engine airplanes is to use a combination of both: a slight sideslip dirties up the airflow enough to create some useful drag, and power is used to maintain the approach angle.
I can't think of a light airplane you can't sideslip, or any airplane you can't sideslip for that matter (perhaps the Mig 15). Sideslipping was used successfully in the Gimli Glider incident, and that was a 767! There are limitations which will be listed in the aircraft documentation, for instance you should not sideslip a C152 above 20 degrees of flap. If I'm flying a C150/152/170/172 I follow that rule.

I don't recall any restrictions on slipping the C152 with flaps. I do recall the 20 degrees of flaps limitation on the C172, however.

A note on carb icing: I have been further spoiled in my training on the DA20's in that they are fuel injected: I've never had to worry about carb heat. But the point on engine cooling is quite valid.

Please update article with authoritative evidence for carb ice with full carb heat

There may be limitations in the aircraft documentation (most aircraft that I have flown do not, although they do exist).

@Dawn: Agreed..

When we learned to fly in low-lift airfoil tailwheels, with radial or early flat-4 engines, we always expected an engine failure. Patterns were close-in, power was idled turning base (pace winds), and landings were made 3-point in a full stall. And the trainers (eg Cub, Citabria) didn't have flaps, so you learned slips to landing.
With the advent of nose wheels, better airfoils, and the marked improvement of engines, the rate of non-fuel-exhaustion engine failures declined, and we could make bigger patterns and expect that some power would carry us to the threshold.
What we lost is a sense of what it takes to make it to the runway. And indeed the airplane private PTS only needs to show a simulated engine failure:

The commercial PTS, however, requires that the pilot demonstrate a power-off 180 landing:

which more closely represents how pilots were originally taught, and how tailwheel pilots are still taught, especially those flying radials and early trainers, like the Cub.
That being said, although slips to landing are a normal procedure, they are not the recommended procedure for either airplanes or for gliders (almost all of which have some kind of drag device).
My preference (winds permitting):

light tailwheels: power-off 180 to a 3-point
high-drag tailwheels: power-off below 300ft to a 3-point
nosewheels: low-power (1500 rpm or 15")
gliders: sufficient use of drag device for a 10:1 approach

In all cases, I am high rather than low, and close in rather than further out in the pattern.
A no-flap landing in an airplane, which is a normal procedure, requires more airspeed because the stall speed is higher, so the approach is flatter and the airspeed is higher.
No flap landing checklists in airplanes do not specify a slip, although slips are still used as necessary. In my airplane, a no-flap landing requires 10 knots higher airspeed because the flaps are so effective.
In an airplane that has not-very-effective landing flaps, such as the DA20 (which I have never flown), the airspeed differential between take-off flaps and  landing flaps would be much smaller, and indeed this is what shows up on the checklist:


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What is the type of nozzle used on the MiG-21 and MiG-27?
Generally supersonic fighters have convergent - divergent nozzles. What is type of nozzle used in MiG-21 and MiG-27?
Also please explain that how in a convergent nozzle where the max velocity in the nozzle is limited to one mach , how can the ac still go supersonic??

I suggest you delete the second part of the question, because it is already answered in the question Peter Kämpf linked and because it is not related to the first part anyway.

Mig-21F, the first version of Mig-21 to be called as such, used a Tumansky R-11F-300 engine, which had a (variable) convergent nozzle. Later versions used Tumansky R-13-300, which was similar to the R-11 and Tumansky R-25-300 which had variable convergent nozzles as well. The Mig-27 used the Tumansky R29B, which has a convergent-divergent nozzle according to the manufacturer's site.
In theory, the aircraft speed is not limited by the exit speed, but the extra speed imparted to a mass of air by the engine (more the $\Delta v$, more the thrust). Basically, there is nothing that prevents an aircraft with convergent nozzle from attaining supersonic speeds, albeit the system is very ineffecient.

If the designer is ready to accept a weight and fuel consumption penalty, he/she can use a supersonic convergent nozzle. Though this is ineffecient, for short duration, this would be acceptable.
Another point to note is that the high exit temperatures means that the sonic velocities in the exhaust are nuch higher than the freestream ones. This means that the difference in speed is there, though the mach number may be less.


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Radial-engine twin with square/straight tail

Apologies for the blurry photo. Digital zoom. It was sent to me by a friend who knows I love planes, but with few other details. Beggars can't be choosers. :)
The photo makes the plane look blue, but my friend says they're pretty sure the plane was mainly polished aluminum.
The friend says that the engines sounded "different". To me, they appear in the photo to be radial engines, but of course I can't be 100% sure because the photo's so blurry.
To me, it looks like an early-era Cessna 310. The nose and tail look right, but as far as I know the 310 was never built with radial engines, and I've never heard of them being retrofitted. The tail seems wrong for the Cessna T-50/AT-17, which AFAIK only had an elliptical tail, and no tip tanks.
It does bear a striking resemblance to the Grumman F7F Tigercat. But that plane has a more rounded vertical stabilizer, and I didn't find any photos of examples that had tip tanks.
Also, my friend tells me that the wings are actually very long, having an aspect ratio approaching U-2 dimensions.
I feel like between the squared-off tail, the tip tanks, the slender aft fuselage, and apparently pointy nose, the aircraft type should be identifiable. Each of those features seems distinctly reminiscent to me of other aircraft, but none that have all of them.
If it helps, the photograph was taken recently in the Seattle area. It was headed ESE, around 2035 UTC today. It doesn't appear to be any of the aircraft in the nearby Flying Heritage & Combat Armor Museum collection. But I would not be surprised if it belongs to some well-known collection in the Pacific Northwest region.

It's a Douglas A-26 (later B-26) Invader.  That's one of the Vietnam era B-26's with the tip tanks added.
This particular airplane is "Sexy Sue", a nicely restored example.

Nice find! Specifically this may be Sexy Sue (warning for some NSFW nose-art), which was in the air today in Washington.

A really nice A-26 flying around town early this afternoon from the Saint George (Utah) Regional Airport. I didn't know there was a restored one in the area. P.S. No tip tanks.


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Why will windshear inop illuminate after landing in an MD-83?
Why will windshear inop illuminate on the annunciator panel after landing or before starting taxi in a McDonnell Douglas MD-83?

The WINDSHEAR INOP light tells the pilots that the Predictive Windshear System cannot work:

System Annunciator Lights
[...]
An amber WINDSHEAR INOP annunciator is installed on the annunciator panel.
  This light illuminates any time the windshear systems detects a fault which
  renders the system inoperative.

(MD-80 FCOM Sec. 16 - Instrumentation / Navigation / Communication - Predictive Windshear System)
In order for this system to function, the radar system needs to be active, which is a hazard to the ground crew:

RDR-4B Radar System Theory
Like all modern radar systems, the RDR-4B operates by emitting short
  intense pulses of microwave energy which are reflected by objects having
  reflective characteristics within the range of the system. The reflected
  signals are processed to produce visual displays that are representative of the
  size, intensity, bearing and distance of the targets. The RDR-4B incorporates
  an advanced microprocessor design which utilizes the Doppler principle to
  identify areas of moderate and higher turbulence as well as low level
  windshear (microburst) activity. The RDR-4B system is designed to operate
  in the windshear mode automatically any time the aircraft is below 1500’
  AGL, at least one engine is running, and the transponder is not in OFF or
  STBY, REGARDLESS OF RADAR MODE SELECTED. The system also
  operates in the windshear mode below 1500’ AGL using an alternate scan
  technique if the radar is operating in any mode (WX / TURB, WX, MAP). The
  windshear mode is activated at 2300’ AGL. However, no alerts or displays
  are annunciated above 1500’ AGL.
WARNING:
  Failure to return the transponder to STBY after landing or
  selecting any mode except STBY prior to leaving the ramp area
  allows the radar to operate in the windshear mode creating a
  radiation hazard to personnel on the ground. The RDR-4B
  radiation hazard area extends 13.4 feet from the radar antenna
  in a 120 degree arc left and right of the aircraft centerline.
  This hazard exists even if the radar mode is selected OFF or
  TEST.

(MD-80 FCOM Sec. 16 - Instrumentation / Navigation / Communication - Predictive Windshear System)
After landing, the pilots will switch the transponder to STBY in order to deactivate the radar system before reaching the apron (where ground crews are working). This will disable the Predictive Windshear System and causes the WINDSHEAR INOP light to illuminate.

Is it just my unfamiliarity, or is that not the safest way of implementing emission control? Having the radar continue to radiate unless the crew flips the transponder switch sounds a bit unsafe compared to, e.g., having the weight-on-wheels signal inhibit the radar.

@AEheresupportsMonica You don't always want to inhibit the radar on the ground since you would otherwise not be warned of a windshear during the takeoff roll. But I agree, this is probably not the best way of implementing it...

Yeah, that's fair. But it could be done by arming the system such as, with WoW off, it going on and remaining on for 5 seconds, would shut the radar down. Makes me wonder how this is handled in more modern aircraft.


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What regulations apply to changing liveries on private jets in the US?
Things like the manufacturer's livery, do they need to follow that?
Anything else that will be required when purchasing a new jet and changing the paint to the new owner's choice and requirements.

Usually requires a new weight and balance. There are a number of regulations, are you asking about them regarding style? Application and removal? Colors?

Yes, if it does not conform to the manufacturer's original requirements. No, to the removal and application or colour. The point you make about the weight and balance, I'm sure is something new owners do not immediately consider.

I do understand that having a new colour that's very dark, can also be what changes a planes weight and balance, maintenance (oil streaks are not as obvious), cost to apply and resell value could take a hit.

The only requirement is the height of the registration number, 12" if flying internationally (from the US anyway), 2" I think if staying domestic, and maybe new weight & balance - but usually a layer of paint and primer is taken off, and a new layer is put on, so the weight change is minimal.  Any control surfaces that were removed may need rebalancing.  Colors & schemes are at the whim of the owner(s).


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Is it harder to get a first pilot certificate in a motorglider compared to a normal powered aircraft (near St. Paul, MN.)?
Is it harder to get a first pilot certificate in a motorglider (glider - self launch) vs. normal powered aircraft near St. Paul, MN.
It seems like a self launch glider certificate would be a great way to start because of better stick and rudder skills, lower age requirements (for my son), cheaper operating costs, glider hours apply toward power aircraft requirements, etc but I'm concerned that it might be a bad path because it appears to be rare and hard to find instruction near St. Paul, MN.

It will be harder to get initial training in a motor glider near St. Paul, because motor gliders are kind of rare around here.
However, consider this:
Instruction in a un-powered glider is mind-bogglingly cheap compared to power instruction. And it has the other mentioned benefits - stick and rudder skills, low age limits, etc.
After getting a first pilot certificate in a non-motor glider (and after suitable further training), one may add Motor Glider ("self-launch") privileges with only an instructor endorsement - no Designated Pilot Examiner needed!
One may also add Light Sport - Airplane privileges with a two-instructor endorsement process - also no Designated Pilot Examiner needed! If you or your son want to fly LSAs, starting with a glider rating can be a great bargain.
And you have options! Some clubs: Minnesota Soaring Club in Stanton, Red Wing Soaring Association in Osceola (* note NOT in Red Wing, despite the name); and a commercial operation: Cross Country Soaring in Faribault. Not to mention any private instructors you may ferret out in the community.
I personally am a member of RWSA and hope to get my self-launch and LSA endorsements one of these days, but I'm having plenty of fun soaring in towed gliders in the meantime.

If you see this in time, https://stpaul.ce.eleyo.com/course/9539/winter-2020-adult/private-pilot-glider-ground-school may be of interest: A glider ground school hosted by MSC and RWSA.

Though it is not part of your question, why are you not considering the conventional (Aerotow) soaring path for your son.  My glider club, The Skyline Soaring Club has a rotating group of young folks that take advantage of the instruction the club offers.  Last year, we had several fourteen year olds solo and a number of sixteen year olds have gotten their glider ratings through our club.
It looks like there is a club based in the St Paul area, the Minnesota Soaring Club, that likely does a similar thing.  My suggestion is that you strongly consider this path for your son.


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What is the difference between "Type Certificate" and "Certificate of Airworthiness" for an aircraft?
I want to know what exactly is "Type Certificate" and "Certificate of Airworthiness" means for an aircraft.

A Type Certificate is a certificate that the FAA gives the manufacturer of an aircraft, certifying the design of the aircraft. So for instance, Cessna Aircraft Company of Wichita, KS holds a Type Certificate for the Cessna 172. Notice that the certificate specifies what components make a Cessna 172, what its limitations and performance specifications are, and so on. When Cessna makes a 172, that aircraft has to conform to this specification. Moreover, only aircraft that meet this specification are certified as a 172. Which is why, if you make a major modification to a certified aircraft, it requires an STC-- a "Supplemental Type Certificate," to confirm that with the new equipment, the aircraft design is still airworthy and the limitations are accurate. But there is only one Type Certificate for an unmodified Cessna, and it is issued to Cessna, Inc.
On the other hand, an Airworthiness Certificate is issued for each aircraft individually and certifies that this here particular airplane is airworthy. They can be revoked if the airplane undergoes, for instance, an accidental major airframe modification (or indeed, an uncertified major alteration of any kind or if for some reason the FAA has reason to believe the aircraft is no longer airworthy). Each aircraft has its own Airworthiness Certificate that is displayed in the passenger compartment, and thus there are as many Airworthiness Certificates for Cessna 172's as there are airworthy 172s.

If I could upvote twice I'd do it for your accidental major airframe modification!

Or even revoked without modification, if something new is discovered about the existing components (e.g. failure modes)

@Pavel the only way to improve it would be a phrase with an appropriate acronym  such as CRUMP, MUNG, CAUFU ...

accidental major airframe modification?  Such as a Rapid, Unscheduled airframe modification?


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Can I land at an uncontrolled airport under class C without talking to ATC?
In this situation, I would be flying from Richmond Executive-Chesterfield (FCI) to New Kent Co (W96).
Can I land at an uncontrolled airport under class C without talking to ATC?
Picture source: SkyVector

If your goal is to reduce radio chatter, wait until you're ready to take-off, and pick them up from the hold short line. I'm assuming that you can get reception that close, even on the ground.  Or if you really don't want radio chatter, fly a dog-leg to the east at 1,300ft MSL. A third (second ATC-less) option would be climb west and turn around and  fly over class-C and then come back around under the other side, but that seems really bothersome.

It looks to me like New Kent is entirely below the shelf of the class C space.   You don't need to go through the Class C Core at all, so I don't see that you need to speak to them.  The detour to avoid the core looks minimal
You can see the shelf height shown as 42/14, meaning that the class C space starts at 1400 feet, and goes up to 4200 feet.   Just stay below the shelf, at about 1100 feet. At that altitude, pay extra attention to any obstacles like radio antennas!  I do see several obstacles going up to 500 / 600 feet!
If you want to let them know of your intentions, I'd just say:
"Potomac Approach: N12345, Departing Richmond Exec, to New Kent, VFR below Class C.  On Frequency."
They will likely respond with:
"N12345: Proceed as requested. Maintain VFR"

Link to Flight Diagram

I would just proceed under the shelf and pick up flight following enroute. If you're under the shelf, you don't have to talk to ATC at all, however I think it would be a good idea as you'll be crossing the extended centerline of all three runways at some point during your flight. Once you get flight following, you can gain altitude and possibly cut straight through the center ring as well.


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Could a variable sweep aircraft also use negative angle?
Variable sweep on fighter aircraft is a bit out of fashion, but seems to a worthwhile option to adjust the wing to the current speed and needed lift. All this is bought with complexity and weight of the system.
Would it be possible to build a variable sweep aircraft that goes low speed and in a dogfight into a forward swept wing configuration like the Su-47 and high speed in a rearward swept wing?

Image of Su-47 credit to Wikipedia (Leonid Faerberg)

What is the aircraft in the photo?

It's a Su-47. I edit my post accordingly.

Yes it could, but don't hold your breath.
Forward sweep means that the aeroelastic forces will twist the wing at high lift into an increased angle of attack, so such a wing needs to be stiff in order to avoid divergence (PDF!). Also, aileron effectiveness is excellent, so a forward-swept configuration is a good choice for dogfighting.
Since backward sweep is mostly helpful at trans- and supersonic speed, swing wings were the right answer when very high top speeds (Mach 2+) needed to be combined with high loads at take-off and short field length requirements. When flying ever faster went out of fashion in the 1970s, the attractiveness of variable sweep disappeared.
Forward sweep helps both in air combat and in transsonic flight, so there is little advantage in a variable-sweep configuration with forward sweep. An aircraft optimised for air combat has little need to fly Mach 2+, so the moderate sweep angle is a good choice for most of its flight time. Also, the aeroelastic instability increases with sweep angle, so more than moderate forward sweep needs a very stiff and heavy wing.

Aircraft with forward-swept wings also have negative yaw-roll coupling (yawing in one direction causes the aircraft to roll out of the yaw, rather than into it (as is the case with aircraft with backward-swept wings)), which could be useful in certain situations.

@Sean: That only means their optimum dihedral is higher than that of backward swept wings. Dihedral is used to adjust the overall roll response to yaw, and sweep only changes the starting condition for selecting dihedral.

Yes. Variable sweep airplanes exist and it shouldn't be a problem to design a system able to sweep the wings forward and rearwards. However, the few aerodynamic advantages of the forward swept wing at low speeds doesn't justify the added complexity, weight and loss of space inside the fuselage.


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Can I do an instrument rating checkride in an experimental aircraft?
The EAA has a document that strongly suggests that IFR operation in Experimental Aircraft is legal.  The necessary equipment is described in 91.205.  Provided all this is met, as well as all other IFR requirements (e.g., pitot check, appropriate engine, etc.), I think instrument rated pilots are ok to fly IFR in an experimental.
However, in a question related to a checkride in an LSA, Can I do an IFR checkride in an airplane that isn't certified for IMC? , I learned about another concerning aspect.  It says:

the Instrument Practical Test Standards (FAA-S-8081-4E PTS Instrument):  Aircraft and Equipment Required for the Practical Test The instrument rating applicant is required by 14 CFR part 61 to provide an airworthy, certificated aircraft for use during the practical test.

[my boldface].  Putting all this together suggests that I can train and fly in true IMC in IFR in an experimental aircraft, but I cannot take my checkride in one.  Is this interpretation incorrect?  Are there (m)any cases in which checkrides were done in experimentals?
PS: I sometimes wonder whether we are training to become pilots or lawyers...

That word “certificated” seems a bit nebulous. When pilots talk about “certificated” aircraft they are usually referring to aircraft with a type certificate. But every aircraft must have some kind of airworthiness certificate, so it’s unclear in this context what is meant, at least to me. It doesn’t specifically say in that paragraph that a SAC doesn’t suffice.

Yes, but only if the examiner agrees. 61.45 says:

(a) General. Except as provided in paragraph (a)(2) of this section or
  when permitted to accomplish the entire flight increment of the
  practical test in a flight simulator or a flight training device, an
  applicant for a certificate or rating issued under this part must
  furnish:
(1) An aircraft of U.S. registry for each required test that—
[...]
(ii) Has a standard airworthiness certificate or special airworthiness
  certificate in the limited, primary, or light-sport category.
(2) At the discretion of the examiner who administers the practical
  test, the applicant may furnish—
(i) An aircraft that has an airworthiness certificate other than a
  standard airworthiness certificate or special airworthiness
  certificate in the limited, primary, or light-sport category, but that
  otherwise meets the requirements of paragraph (a)(1) of this section;

This article describes an IR checkride in a Van's RV6.


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Is there any source or database from which we can find out the total number of military aircraft sold globally every year?
There are a few online databases that sheds light on the number of commercial jets that countries, airlines purchases every year.
Is there any database that provides similar figures for military aircraft sold annually around the world every year ? In case exact figures are not available, approximates will do.

A lot of governments make spending data public, SR-71 style stuff aside you can likely find the data if you are willing to go through enough reports...

@Dave     Does such a database exist for the US military?

I doubt an exact number is available since that would pose a national security risk. It would have to be approximations extrapolated from annual defense budgets.

@CarloFelicione Ok ! Approximates will do

As a "database", probably not. Buried deep within appropriations and/or budget bills of various countries, you'll probably be able to come up with reasonably close numbers. My guess is you'll need plenty of caffeine to keep yourself awake reading deep enough to find it all.